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Chain Rattling Sound at WOT above 4.5k RPM

FordMustacheGT

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I noticed a rattling sound similar to a loose/rattling chain when I’m at/near WOT above 4.5k rpm. All of the other threads talk about a chain rattling sound at lower RPMs, I haven’t noticed this at all. I only hear this noise at the upper end of the range and only when the throttle is >85% open.

Does anyone have any ideas on what I should look at first? I ordered a black stone oil analysis kit, when I get the kit I’ll change the oil and send a sample out for analysis.

I don’t have any check engine lights, I’d assume my knock sensor would pick up any knocking and throw a code but I’m not completely sure how that is programmed to function.

The first time I noticed this noise was after a track/autocross day. This was set up a little different than normal autocross; it took place on a small track and we basically just ran as much as we wanted for an hour and a half. At one point I think I did a run for around 40-50 min straight of mostly right turns. Around this time I also notice the diff making a bit more noise, like the backlash between the gear sets opened up a little bit. I’m not as worried about that, but I’m just making a mental note about that noise.
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FordMustacheGT

FordMustacheGT

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Bumping this, my life got a little busy and I set this to the side but I started digging into this issue again. I’m sort of grasping at straws, I’d appreciate any suggestions for things to look into.

I made a recording that can be found here: note that this is recorded with a microphone mounted to the license plate frame.

A bit about my car: 2015 GT Premium, non-performance pack. Magnaflow Tru-X resonator and SLP Loudmouth II mufflers. Otherwise stock power train, on a stock tune as far as I know.

So far I’ve tried the following things, which haven’t worked:
- tightened parking brake cable - found this to be loose
- inspected exhaust for leaks at joints - no obvious signs of leaks
- applied DynaMat to the engine-transmission spacer plate (https://www.mustang6g.com/forums/threads/engine-transmission-plate-noise-fix.115718/)
- replaced passenger-side flex pipe - I found the braided section had frayed and broken at one of the crimps)
- replaced magnaflow tru-X with the same model - the exhaust shop thought that the packing/mesh might have deteriorated
- installed quite a bit of dynamat/aluminum tape to the heat shielding in order to try to dampen/eliminate any resonance
- tightened all front under tray and side skirt fasteners

I may just start to pull the entire exhaust system apart and reinstall using a muffler sealant at each joint, but I don’t see any visible signs of an exhaust leak. It’s driving me nuts!
 
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